Electric cable



Patented May 6, 1930 UNITED STATES PATENT OFFICE JOHN FRANCIS WATSON, OFABBEY WOOD, PHILIP VASSAR HUNTER, OF LONDON, AND

ALFRED EDGAR WILSON, OF BROMLEY, ENGLAND ELECTRIC CABLE Applicationflledlanuary 12, 1928, Serial No.

This invention relates to electric cables, particularly to high tensioncables with one or more insulated conducting cores.

In the specification of our U. S. Patent N o.

5 1,743,506, patented January 14, 1930, electric cables are described inwhich the di-electric is formed with a passage which, in the completedcable, surrounds the conductor and is of suificient diameter to allowsome movement 10 of that conductor. Various ways in which such a passagemay be formed are also described.

The present invention has the same object in view and is concerned withanother way in which the desired passage may be made or, in other words,the desired freedom of movement of the conductor obtained.

It is to be understood that the term conductor as used in thisspecification refers to that part of the core which is surrounded by thedi-electric; it may comprise strands or members of non-conductingmaterial in addition to the metallic conducting members.

According to the present invention the conbe reduced, after the cable ismade up, sufficiently to give the desired freedom of axial and/or radialmovement between it and the di-electric. Thus instead of forming thepassage initially it is produced by a reduction of the diameter of theconductor.

This reduction may be effected in any convenient way as, for example, bylaying up the conductor with some of its strands, say in the outer layeror layers, made so that they are compressible or deformable, forinstance, by applying tension to the conductor. These strands may bemade of jute or loosely stranded paper, string or other similar sub- 40stance, but are not necessarily of non-conducting material.

The tension or pull, when such force is used to reduce the diameterof-the conductor, may be ap lied prior to jointing after the cable islai or to lengths of the cable at any stage before la ing so that theclearance whlch is theiob ect of the invention is produced.

It is to be understood that in carrying out 6' this invention thepaperor other di-ele ctric ductor is so constructed that its diametermay- 246,292, and in Great Britain April 25, 1927.

may in some instances be directly around the conductor, although inother instances a tubula'r sheath, such as that mentioned in thespecification of the pending. application aforesaid, may be used to forma wall for the passage when formed by the reduction of the externaldiameter of the conductor.

Such tubular sheath when present may with,

the diameter of its conductor is reduced.

Figure 21s a similar view after tension has been applied to theconductor,

Figures 3 and 4 are'cross-sections of two other constructions of cable,

F igures 5 and 6 are views similar to Figures 1 and 2'but with theconductor constructed in a difl'erent Way,

Figure 7 is a plan with parts broken away of another construction ofcable,

Figure 8 is a cross-section of a concentric cable, and

Figure 9 is a plan with port-ions away of a three-core cable.

In Figures 1- to 7 the di-electric is indibroken cated at A and willusually be of paper, and

B represents an outer lead sheath which may or may not be present anddoes not itself form part of the present invention.

In Figure 1 the conductor of .thecable is made by conducting members Claid up round a central member ,'D of some compressible or deformablemateriah By applying tension to the conductor its diameter is reduced asshown in Figure 2, leaving a passage or space between it and thesurrounding di-electric A.

In the cable shown in Figure 3 the conducting strands C of the conductorare laid up with other strands D of compressible ordeformable materialand in Figure 4:- similar compressible or deformable strands D are laidup with and under the outer layer of conducting strands C Each of thesefigures shows the cross-section of the cable as made and before tensionis applied to the conductor. When that tension is'applied the passage orspace is formed Within the dielectric as described with reference toFigures 1 and 2.

It will be appreciated that, when the wires or conducting strands arelaid up in helical form, the application of tension to the ends of thesewires will tend to extend the helix and will thereby decrease thediameter of the helix, forcing the conducting strands into thecompressible or deformable material so that the diameter of the entireconductor consisting of the members C and D is materially reduced. Ifdesired, this tension can be applied to the entire conductor includingthe deformable material, but it will be apparent that thedecreas'e indiameter of the conductor is efl ected primarily by the extension of thehelix consisting of the conducting strands rather than. by the extensionand deformation of the cross-section otthe individual strands.

InFigures 5 and 6 the conducting members C? are segmental and laid upround a central member I)? of compressible or deformable' material.Figure 5 showsthe cable in section before the diameter of the conduc toris reducedby applying tension to it, and Figure 6 is a crossssection ofthe cable after the tension has been applied and the passage formedbetween the di-electric and the conductor. I 5 v Figure 7 shows aportion of a cable having conducting strands'C laid up roundcompressible or deformable material D as, for instance, in Figures 1 and'2, but inside the dielectric A is a tubular sheath E formed ofover-lapping strip constituting the outer wall ing to this invention.The inner conductor is made up ofconducting strands G and strands ofcompressible or deformable materiall) and is surrounded by di-electric AThe outer I conductor is made up of conducting strands able material D.The diameter of each conductor is reduced by applying tension to it andthe outer wall of the passage or space thus formed is constituted by atubular sheath E to which the di-eleotric A is applied. All threeinsulated cores may be surrounded by di-electricasat A and the whole maybe enclosed in a leadsheath B The tubular sheath E or E when provided,may be of any desired construction'and may be of metal or ofnon-metallic material. In the latter case it is preferred to render itsinner surface conducting by coating it with metal foil. 1

It is to be understood that the passage or space formed between thedi-electric and the conductor will not be an air space but will befilled with the oil or compound with which the cable is impregnated. Ifany oil or compound is withdrawn when tension is applied to theconductor it will be made good when the lengths are laid and jointed.

What we claim as our invention and desire to secure by Letters Patentis 1. A method of manufacturing an electric cable which consists inlaying up the strands of the conductor so that its diameter can bereduced by applying tension to it, applying a covering of di-electricaround the conductor and then applying tension to the conductor toreduce its diameter and form a space .between it and the surroundingdi-electric.

2. A method of manufacturing an electric cable which consistsinylayingup the strands of the conductor so that its diameter can bereduced by applying tension to it, applying a tubular sheath around theconductor, applying a covering of dielectric around the tubular sheathand then applying tension to the conductor to reduce its diameter andform a space between it and the tubular sheath so that the latterwillcontinue to support the dielectric after the diameter of theconductor has been reduced.

In testimony whereof we have signed our names to this specification.

JOHN FRANCIS WATSON. PHILIP VASSAR HUNTER. ALFRED EDGAR WILSON.

